Kenlowe do a pre-heater that plugs into your domestic leccy, Eberspacher do an even more expensive one that runs on fuel tapped off the vehicle, means the engine is warm when you get in....but no help if your seals are shot and a howling gale comes in round the doors, through the front vents and the various holes in the bulkhead !
....check that the heater hoses inside the dash are actually connected. They are not that well joined up and previous fiddling with the electrics can have dislodged them, meaning the warm air does not all get to the windscreen etc...
